Check your internet connection, is it stable? If you're using a wireless router, is that functioning properly? If you've answered yes, then lets start looking at your account status.
If you've set up your account, did you check your email to finish the "email confirmation" of the process? I tend to forget to do that on other websites that require that xD
If you've checked off on all of that, there's always the possibility you left capslock on when you typed your password in while registering, but you forgot (I've done that too LOL). If not....then I dunno :C